Although there is a record population of endangered whooping cranes at their wintering grounds at Aransas NWR in Texas, it has been a â€œfrustrating winter.â€
The known population of 270 wild cranes â€“ 232 adults and 38 juveniles â€“ is a record number, according to Tom Stehn, the whooping crane coordinator with the U.S. Fish and Wildlife Service.
However, â€œthe total numbers are a disappointment,â€ he said.Â â€œThirty-eight juveniles added to the population of 266 could have resulted in 304 whooping cranes arriving at Aransas.Â If 270 is a reasonable estimate of what did arrive, it means 34 whooping cranes, or 12.8% of the flock, died between spring and fall, 2008.â€
Conditions not documented at Aransas in 26 years, have made it a difficult wintering season along the gulf coast of Texas. In a update, Stehn noted:
- 1) â€œNatural marsh foods were at low levels due to the prolonged drought.Â Blue crabs were present initially, (an important food source for whooping cranes that make up 80-90% of their diet when available), but crab numbers dropped off through November.Â Blue crabs were scarce throughout December and January as tides were lowered by low pressure systems and most
of the remaining crabs moved out into the deeper bays.
- 2) â€œThe fall wolfberry crop was very low, a food that the cranes normally rely on heavily.Â Thus, the cranes were ill-prepared to face the scarcity of crabs.
- 3)Â â€œMarsh salinities have remained above the threshold of 21 parts per thousand that forces cranes to seek out fresh water to drink.â€
So far this winter, five whooping cranes are believed to have died, Stehn said. A necropsy of the two carcasses recovered showed the birds were emaciated, indicating a lack of sufficient food. During a typical winter, there is none, or just one, death.
â€œWhooping cranes are being seen in unusual places this winter, Stehn said.
â€œMany have left the salt marsh and are feeding on uplands.Â Up to four cranes foraged daily in the farm fields north of the refuge through December.Â A record 21 whooping cranes are wintering on the Lamar Peninsula utilizing game feeders in locations where we have never seen cranes before.
â€œDue to the food shortages, the unusual distribution of cranes observed, and the two emaciated crane carcasses recovered, supplemental feeding of whooping cranes with corn on the Aransas / Matagorda Island NWR complex has been initiated and will be continued for at least one month.Â Prescribed burns have also been conducted to provide additional foraging opportunities.â€
These actions have been taken by refuge officials to help nourish the cranes, and provide a boost to their physical condition to avoid potential nesting problems this breeding season.
â€œResearch done by Dr. Felipe Chavez-Ramirez in 1994 documented that up to 37% of the whooping cranes failed to nest following a poor blue crab winter at Aransas NWR,â€ Stehn wrote in his report.
Other unexpected behavior has been juvenile cranes separating from their parents.Â This occurred with two birds at Aransas. A third bird spent the late autumn and early winter in south-central Nebraska, departing in early December for Oklahoma, and remaining there until late January.
Crane biologistsâ€™s currently do not know the whereabouts of any of these birds. Juveniles typically remain with their parents through the winter season.
The whooping cranes will remain in the area of Aransas NWR until they depart sometime in the March for the 2500 mile flight to their ancestral breeding grounds at Wood Buffalo National Park, in the Northwest Territories Province of Canada.
The group of cranes in Texas is a population distinct from the cranes that are the result of a program to reintroduce this species to the eastern states.
â€œThere are now 73 migratory whooping cranes in the wild in eastern North America,â€ according to Fish and Wildlife Service officials, â€œincluding the first whooping crane chick to hatch in the wild in Wisconsin in more than a century.Â Many of these cranes have settled into their wintering locations in parts of the Southeast, including Georgia, Alabama, South Carolina, Tennessee, and Florida. State partners from Wisconsin, Illinois, Kentucky, Tennessee, Alabama and Georgia provided strong support throughout the migration.â€
A group of seven cranes, led by an ultra-light sponsored by Operation Migration, recently arrived at St. Marks NWR in Florida, after a successful journey of more than 1200 miles from their summering grounds at Necedah NWR in Wisconsin. Additional cranes are at Chassahowitzka NWR, north of St. Petersburg.